local filters = require "util.filters";

local st = require "util.stanza";

module:depends("csi");

local function presence_filter(stanza, session)

	if getmetatable(stanza) ~= st.stanza_mt then

		return stanza; -- Things we don't want to touch

	end

	if stanza._flush then

		stanza._flush = nil;

		return stanza;

	end

	local buffer = session.presence_buffer;

	local from = stanza.attr.from;

	if stanza.name == "presence" and (stanza.attr.type == nil or stanza.attr.type == "unavailable") then

		module:log("debug", "Buffering presence stanza from %s to %s", stanza.attr.from, session.full_jid);

		buffer[stanza.attr.from] = st.clone(stanza);

		return nil; -- Drop this stanza (we've stored it for later)

	else

		local cached_presence = buffer[stanza.attr.from];

		if cached_presence then

			module:log("debug", "Important stanza for %s from %s, flushing presence", session.full_jid, from);

			stanza._flush = true;

			cached_presence._flush = true;

			session.send(cached_presence);

			buffer[stanza.attr.from] = nil;

		end

	end

	return stanza;

end

local function throttle_session(event)

	local session = event.origin;

	if session.presence_buffer then return; end

	module:log("debug", "Suppressing presence updates to %s", session.full_jid);

	session.presence_buffer = {};

	filters.add_filter(session, "stanzas/out", presence_filter);

end

local function restore_session(event)

	local session = event.origin;

	if not session.presence_buffer then return; end

	filters.remove_filter(session, "stanzas/out", presence_filter);

	module:log("debug", "Flushing buffer for %s", session.full_jid);

	for jid, presence in pairs(session.presence_buffer) do

		session.send(presence);

	end

	session.presence_buffer = nil;

end

module:hook("csi-client-inactive", throttle_session);

module:hook("csi-client-active", restore_session);